The present invention relates to a radiation detection device.
The word "radiation" is understood to more particularly mean infrared, X or .gamma. radiation.
Particular applications of the present invention occur in the field of thermal imaging and e.g. applies to the manufacture of a converter of infrared radiation into visible radiation.
As a result of the miniaturization of integrated circuits, factors limiting the sizes of systems having such circuits are at present the assembly and the interconnections of said circuits. Various methods are known for producing complex, dense systems from integrated circuits.
A first method consists of eliminating the packages of said circuits or chips and directly hybridizing said chips, by means of welding microbeads, to multilayer substrates making it possible to produce interconnections between the chips.
This first method known as the flip chip method makes it possible to hybridize hundreds of chips on ceramic substrates, i.e. the so-called multichip module. This method is described in U.S. Pat. No. 4,202,007.
A second known method, called the "three-dimensional" method makes it possible to bring the interconnections into a reduced volume.
For example, said second method consists of bonding the chips to one another and forming appropriate electrical connections on the edge of the resulting block, so as to be able to interconnect the different chips by their edges, as can be gathered from:
(1) "Packaging takes on a new dimension", European semiconductor conductor, March 1993, p.21; PA1 (2) French patent application 8905542 of Apr. 26, 1989 (cf. also EP-A-395488 and U.S. Pat. No. 5,131,584). PA1 a detection array for receiving the radiation and for supplying signals representing said radiation and PA1 a circuit for reading signals supplied by the detection array, PA1 said device being characterized in that the reading circuit incorporates a block having at least one stack of integrated circuits constituting elementary reading circuits, in that the device also has an electrical output component electrically connected to the reading circuit and in that the detection array and said component are respectively fixed to two separate faces of the block, in that the elementary reading circuits are hybridized to one another by welding microbeads and in that the detection array and the electrical component are hybridized to the corresponding faces of the block by welding microbeads. PA1 the integrated circuits constituting the elementary reading circuits are produced, each integrated circuit comprising, on one of its two faces, welding elements for the hybridizing of said integrated circuit to another of the integrated circuits, PA1 said elementary reading elements are hybridized to one another so as to form the stack of integrated circuits, PA1 the gaps between hybridized integrated circuits are encapsulated, PA1 two opposite faces of the stack formed by juxtaposed edges of elementary reading circuits are machined, so as to flatten said opposite faces, PA1 said two opposite faces are treated in such a way as to form there groups of electrical connections intended to be respectively associated with the detection array and the electrical output component and PA1 the detection array and the electrical output component are hybridized to the corresponding faces of the stack.
or hybridize the chips to one another by means of indium microspheres or microbeads, using a self-alignment method, such as is described in:
In the infrared detection field, bidimensional detecting devices are known in which, as is diagrammatically shown in FIG. 2, a detection array 2 for detecting a radiation 4 is directly hybridized, by means of indium microbeads 6, to a reading circuit 8 provided with input-output connections 10.
In the bidimensional device of FIG. 1, each detection pixel is associated with a reading pixel formed on the circuit 8 and whose size is equal to the spacing of the detection array.
In the example of the device diagrammatically illustrated in FIG. 2, the detection pixels 12 of the detection array 2 are distributed in accordance with a spacing of 40 .mu.m in the two directions of the plane and the maximum available surface for the reading pixel 14 corresponding to a detection pixel 12, in the focal plane of the device, does not exceed 40.times.40 .mu.m.sup.2.
At present, the aim is to obtain large surface detection planes having an improved resolution of the image and the aim is also to process in an ever higher performance and more complete manner in the focal plane of a detection device, the signals supplied by the detection array of the device, which also requires a large surface area.
FIG. 3 diagrammatically illustrates the obtaining of a large surface area detection plane by the butt-jointing of elementary detection arrays 16 on a reading circuit 18.
In order to achieve the above objectives, it is necessary on the one hand to reduce the spacing of the detection matrix and on the other have a much larger surface for each reading pixel. Clearly these conditions cannot be simultaneously satisfied in a bidimensional detection device.
Thus, for a given detection pixel size, it is not possible to increase in the detection plane the size of the reading pixel associated with said detection pixel.